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JEE Mains · Maths · STD 11 - 7. binomial theoram

If the sum of the coefficients of all the positive powers of \(x\), in the binomial expansion of \(\left(x^{n}+\frac{2}{x^{5}}\right)^{7}\) is \(939 ,\) then the sum of all the possible integral values of \(n\) is

  1. A \(47\)
  2. B \(57\)
  3. C \(67\)
  4. D \(87\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(57\)

Step-by-step Solution

Detailed explanation

coefficients and there cumulative sum are : Coefficient Commulative sum \(x ^{7 n } \rightarrow{ }^{7} C _{0}\) \(1\) \(x ^{6 n-5} \rightarrow 2 \cdot{ }^{7} C _{1}\) \(1+14\) \(x ^{5 n -10} \rightarrow 2^{2} \cdot{ }^{7} C _{2}\) \(1+14+84\)…
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